1. Field of the Invention
This invention relates to solar heating, and more particularly to a low cost solar heating collector assembly which can be used for a wide variety of domestic or commercial applications.
2. Description of the Prior Art
As is common knowledge, the recent energy crisis caused by acute shortages of conventional fuel sources has precipitated a considerable amount of interest in solar energy as an alternate energy source. Thus, in recent years a wide variety of solar energy heating systems and components have evolved to harness solar energy for use in both domestic and commerical heating and air conditioning applications.
A critical component of all previous solar heating systems is the solar collector employed to absorb solar energy. As is well known, these collectors must not only be thermally efficient, but also strongly constructed since these collectors must withstand the extremes of wide ranges of temperature, wind, rain, and various other elements of weather. A further constraint on the design and fabrication of solar collectors is that the collectors must be relatively inexpensive if solar heating is to successfully compete with conventional sources of energy. Hence, it is commercially imperative that readily available materials be utilized in the fabrication of solar collectors.
Although various heating fluids have been employed by prior solar collectors to absorb impinging solar energy, it appears that liquids, and particularly water, are most commonly employed. Therefore, most solar collectors employ plumbing systems of varying sophistication in which to circulate the heating fluid through the interior of the collector. While serpentine plumbing configurations are often used interior to the collector in order to increase the volume of water within the zone of energy absorption and to reduce the plumbing connections, serpentine plumbing unfortunately is less reliable from a draining standpoint, as is necessary in the event of reduced temperatures. On the other hand other collectors of the prior art have employed heat exchange tubes which extend in substantially parallel spaced apart relationship between headers within the interior of the collector under the glazing. While such a plumbing configuration is significantly more reliable from a draining standpoint, it nevertheless results in a number of plumbing connections within the interior of the collector. These plumbing connections are satistically susceptible to leakage which adversely affects collector performance and for repair requires virtually complete disassembly of the individual collector, in order to remove the glazing to make the connections accessible.
A further consideration in the design of solar collectors is the solar to thermal energy conversion effectiveness of the individual collector panels. This performance characteristic is generally controlled by using an energy absorbing surface with a predetermined selectivity, which is discussed in somewhat more detail hereinafter. It is noted, however, that for most domestic applications, energy absorbing surfaces with a relatively low selectivity are acceptable. On the other hand, certain applications, such as air conditioning, do require higher selectivity. For the most part, however, the construction techniques employed in collectors of the prior art have produced a finished product in which it is relatively difficult to precisely match the selectivity of the collector with the required selectivity of the particular application. Since collector selectivity is directly related to collector cost as a result of the different materials employed, the desirability of producing a collector in which the selectivity can be carefully selected is readily apparent.
Yet another important consideration is the ease in which a collector assembly is installed, and the degree of safety afforded to the workmen performing the installation. Since collectors are commonly employed on steeply inclined roofs, it is highly important that the individual collectors of an assembly be prevented from sliding or slipping prior to the rigid fastening of the collector to the roof. However, since in the prior art most collectors are simply nailed or bolted directly to the roof surface, difficulty has been experienced in preventing dangerous collector slippage during installation.
While enumerable solar collectors are found in the prior art, typical examples are found in U.S. Pat. Nos. 3,937,208; 3,980,071; 3,974,822; 4,003,363, 4,011,856; 4,063,545 and 4,066,063.